Device of Handling Periodic CSI Report

ABSTRACT

A communication device for handling periodic channel state information (CSI) reports comprises a storage unit for storing instructions and a processing means coupled to the storage unit. The processing means is configured to execute the instructions stored in the storage unit. The instructions comprise determining at least one field difference between a reference CSI report and at least one periodic CSI report, wherein the at least one periodic CSI report corresponds to at least one component carrier, respectively; transmitting the reference CSI report to a network; and transmitting the at least one field difference to the network.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. Application Ser. No.13/909,091, filed on Jun. 4, 2013, which claims the benefit of U.S.Provisional Application No. 61/659,996, filed on Jun. 15, 2012.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device used in a wirelesscommunication system and related communication device, and moreparticularly, to a device of handling a periodic channel stateinformation (CSI) report.

2. Description of the Prior Art

A long-term evolution (LTE) system supporting the 3GPP Rel-8 standardand/or the 3GPP Rel-9 standard are developed by the 3rd GenerationPartnership Project (3GPP) as a successor of a universal mobiletelecommunications system (UMTS), for further enhancing performance ofthe UMTS to satisfy increasing needs of users. The LTE system includes anew radio interface and a new radio network architecture that provides ahigh data rate, low latency, packet optimization, and improved systemcapacity and coverage. In the LTE system, a radio access network knownas an evolved universal terrestrial radio access network (E-UTRAN)includes multiple evolved Node-Bs (eNBs) for communicating with multipleuser equipments (UEs), and communicating with a core network including amobility management entity (MME), a serving gateway, etc., forNon-Access Stratum (NAS) control.

A LTE-advanced (LTE-A) system, as its name implies, is an evolution ofthe LTE system. The LTE-A system targets faster switching between powerstates, improves performance at the coverage edge of an eNB, andincludes advanced techniques, such as carrier aggregation (CA),coordinated multipoint (CoMP) transmission/reception, UL multiple-inputmultiple-output (MIMO), etc. For a UE and an eNB to communicate witheach other in the LTE-A system, the UE and the eNB must supportstandards developed for the LTE-A system, such as the 3GPP Rel-10standard or later versions.

In detail, when the CoMP is configured to a UE and multiple transmissionpoints, the UE may communicate with the transmission pointssimultaneously, i.e., access a service via all or part of thetransmission points. For example, a transmission point can be an eNB, arelay node or a remote antenna of an eNB (e.g., remote radio head(RRH)). More specifically, an eNB may manage only one transmissionpoint, or may manage multiple transmission points. That is, Cell IDs ofdifferent transmission points may be different (e.g., when being managedby different eNBs), or may be the same (e.g., when being managed by thesame eNB). Thus, signals transmitted between the UE and the transmissionpoints can be easily recovered due to better quality of the signals.

The CA is introduced to the LTE-A system by which more than onecomponent carriers (CCs) are aggregated to achieve a wide-bandtransmission. Accordingly, the LTE-A system can support a wide bandwidthup to 100 MHz by aggregating a maximum number of 5 CCs, where a maximumbandwidth of each CC is 20 MHz and is backward compatible with the 3 GPPRel-8 standard. The LTE-A system supports the CA for both contiguous andnon-contiguous CCs. The CA increases bandwidth flexibility byaggregating the CCs. When a UE is configured with the CA, the UE has theability to receive and/or transmit packets on one or multiple CCs toincrease throughput.

However, when the UE is configured with the CA or the CoMP, the UE mayneed to report a large amount of sets of channel information to the eNB,to communicate with the network regularly. For example, the channelinformation corresponding to multiple component carriers or the channelinformation between the UE and multiple transmission points may beneeded to be reported periodically. The reporting periods of thesemultiple sets of channel state information may be configured to bedifferent, so occasionally two or more sets of channel state informationmight have to be reported at the same time (such event can be seen ascollision). However, due to the limited radio resource, the capacity ofuplink control channels may not be sufficient to simultaneously containmultiple sets of channel state information (CSI). The eNB cannotcommunicate with the UE efficiently, if part of the channel informationis lost due to the collision.

Thus, efficient reporting of multiple sets of channel information is animportant topic to be discussed.

SUMMARY OF THE INVENTION

The present invention therefore provides a communication device forhandling a periodic channel state information (CSI) report to solve theabovementioned problem.

A communication device for handling periodic channel state information(CSI) reports comprises a storage unit for storing instructions and aprocessing means coupled to the storage unit. The processing means isconfigured to execute the instructions stored in the storage unit. Theinstructions comprise determining at least one field difference betweena reference CSI report and at least one periodic CSI report, wherein theat least one periodic CSI report corresponds to at least one componentcarrier, respectively; transmitting the reference CSI report to anetwork; and transmitting the at least one field difference to thenetwork.

A communication device for handling a periodic channel state information(CSI) report comprises a storage unit for storing instructions and aprocessing means coupled to the storage unit. The processing means isconfigured to execute the instructions stored in the storage unit. Theinstructions comprise omitting at least one field in a periodic CSIreport corresponding to a component carrier, when the periodic CSIreport collides with another CSI report; and transmitting the periodicCSI report to a network.

A communication device for handling periodic channel state information(CSI) reports comprises a storage unit for storing instructions and aprocessing means coupled to the storage unit. The processing means isconfigured to execute the instructions stored in the storage unit. Theinstructions comprise dropping at least one first periodic CSI report,when the at least one first periodic CSI report collides with at leastone second periodic CSI report, wherein the at least one first periodicCSI report and the at least one second periodic CSI report correspond toa plurality of component carriers, respectively; and transmitting the atleast one second periodic CSI report to a network; transmitting anindicator to the network, wherein the indicator indicates which CSIreport is dropped or which CSI report is transmitted.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a wireless communication systemaccording to an example of the present invention.

FIG. 2 is a schematic diagram of a communication device according to anexample of the present invention.

FIG. 3 is a flowchart of a process according to an example of thepresent invention.

FIG. 4 is a table of CQI differences and corresponding bit valuesaccording to an example of the invention.

FIG. 5 is a flowchart of a process according to an example of thepresent invention.

FIG. 6 is a flowchart of a process according to an example of thepresent invention.

DETAILED DESCRIPTION

Please refer to FIG. 1, which is a schematic diagram of a wirelesscommunication system 10 according to an example of the presentinvention. The wireless communication system 10 is briefly composed of anetwork and a plurality of user equipments (UEs). In FIG. 1, the networkand the UEs are simply utilized for illustrating the structure of thewireless communication system 10. Practically, the network can be auniversal terrestrial radio access network (UTRAN) comprising aplurality of Node-Bs (NBs) in a universal mobile telecommunicationssystem (UMTS). In another example, the network can be an evolved UTRAN(E-UTRAN) comprising a plurality of evolved NBs (eNBs) and/or relays ina long term evolution (LTE) system, a LTE-Advanced (LTE-A) system or anevolution of the LTE-A system.

In one example, the network and the UEs may support coordinatedmultipoint (CoMP) transmission/reception, and the UEs can communicatewith transmission points (TPs) in the network according to the CoMP. Indetail, the CoMP can be classified into two main categories: JointProcessing (JP) and Coordinated Scheduling/Beamforming (CS/CB). A maindifference between the JP and the CS/CB is that data of the UE isavailable at all the transmission points when the JP is configured (i.e.enabled), while the data of the UE is only available at a serving point(i.e., serving cell) when the CS/CB is configured. The JP can be furtherclassified into two categories: joint transmission and dynamic pointselection. When the joint transmission is configured, the data of the UEcan be transmitted from multiple transmission points (e.g., coherentlyor noncoherently) to the UE to improve signal quality and/or cancelinterferences. When the dynamic point selection is configured, the dataof the UE is transmitted from only one of the transmission points (e.g.,according to a choice or suggestion of the UE) to the UE to improve thesignal quality and/or avoid the interferences. On the other hand, whenthe CS/CB is configured, the data of the UE is only transmitted from theserving point to the UE, while other transmission points may adjustscheduling (e.g., stop their transmissions), or adjust beamforming(e.g., move their beams) to mitigate the interferences. In addition, theCoMP may also be a dynamic point blanking (DPB). In another example, thenetwork and the UEs may support carrier aggregation (CA), and the UEscan communicate with the network via multiple component carriersaccording to the CA.

Furthermore, the network can also include both the UTRAN/E-UTRAN and acore network, wherein the core network includes network entities such asMobility Management Entity (MME), Serving Gateway (S-GW), Packet DataNetwork (PDN) Gateway (P-GW), Self-Organizing Networks (SON) serverand/or Radio Network Controller (RNC), etc. In other words, after thenetwork receives information transmitted by a UE, the information may beprocessed only by the UTRAN/E-UTRAN and decisions corresponding to theinformation are made at the UTRAN/E-UTRAN. Alternatively, theUTRAN/E-UTRAN may forward the information to the core network, and thedecisions corresponding to the information are made at the core networkafter the core network processes the information. Besides, theinformation can be processed by both the UTRAN/E-UTRAN and the corenetwork, and the decisions are made after coordination and/orcooperation are performed by the UTRAN/E-UTRAN and the core network. AUE can be a mobile phone, a laptop, a tablet computer, an electronicbook or a portable computer system. Besides, the network and the UE canbe seen as a transmitter or a receiver according to direction, e.g., foran uplink (UL), the UE is the transmitter and the network is thereceiver, and for a downlink (DL), the network is the transmitter andthe UE is the receiver.

Please refer to FIG. 2, which is a schematic diagram of a communicationdevice 20 according to an example of the present invention. Thecommunication device 20 can be a UE or the network shown in FIG. 1, butis not limited herein. The communication device 20 may include aprocessing means 200 such as a microprocessor or Application SpecificIntegrated Circuit (ASIC), a storage unit 210 and a communicationinterfacing unit 220. The storage unit 210 may be any data storagedevice that can store a program code 214, accessed and executed by theprocessing means 200. Examples of the storage unit 210 include but arenot limited to a subscriber identity module (SIM), read-only memory(ROM), flash memory, random-access memory (RAM), CD-ROM/DVD-ROM,magnetic tape, hard disk and optical data storage device. Thecommunication interfacing unit 220 is preferably a transceiver and isused to transmit and receive signals (e.g., messages or packets)according to processing results of the processing means 200.

Please refer to FIG. 3, which is a flowchart of a process 30 accordingto an example of the present invention. The process 30 can be utilizedin the UE shown in FIG. 1, for handling multiple channel stateinformation (CSI) reports (i.e., CSI processes). The process 30 maybecompiled into the program code 214 and includes the following steps:

Step 300: Start.

Step 302: Determine at least one field difference between a referenceCSI report and at least one CSI report.

Step 304: Transmit the reference CSI report to the network.

Step 306: Transmit the at least one field difference to the network, totransmit the at least one CSI report to the network, respectively.

Step 308: End.

According to the process 30, the UE first determines at least one fielddifference between a reference CSI report and at least one CSI report.Then, the UE transmits the reference CSI report to the network, andtransmits the at least one field difference to the network, to transmitthe at least one CSI report to the network, respectively. In otherwords, for a CSI report, the UE transmits a field difference between theCSI report and the reference CSI report to the network, instead oftransmitting the complete CSI report to the network. The fielddifference may include one or more difference values betweencorresponding fields of the CSI report and the reference CSI report.Thus, overhead needed for transmitting the CSI report can be reduced.

Realization of the process 30 is not limited. For example, the at leastone CSI report may correspond to at least one component carrier,respectively. That is, when the UE communicates with the network viamultiple component carriers according to the CA, the UE needs to feedback the CSI reports corresponding to the component carriers to thenetwork. After the reference CSI report is determined, the UE only needsto transmit the field differences between the reference CSI report andthe CSI reports to the network. In another example, the at least one CSIreport may correspond to at least one transmission point in the network,respectively. That is, when the UE communicates with multipletransmission points in the network according to the CoMP, the UE needsto feed back the CSI reports corresponding to the transmission points tothe network. In this situation, the CSI reports may include channelinformation between the UE and the transmission points. Similarly, theUE only needs to transmit the field differences between the referenceCSI report and the CSI reports to the network. In another example, theat least one CSI report may correspond to at least one CoMPconfiguration, respectively, wherein a CoMP configuration may be thejoint transmission, the dynamic point selection, the CS/CB or thedynamic point blanking. In addition, different CSI reports maycorrespond to the same CoMP configuration with the same, partlydifferent or different realizations.

Note that detail of a CSI report mentioned above is not limited. Forexample, the CSI report may include one or more fields which include aChannel Quality Indicator (CQI), a Precoding Matrix Index (PMI), a RankIndicator (RI) and/or a Precoder Type Indicator (PTI). In addition, theCSI reports may be transmitted in the same subframe or differentsubframes, and is not limited herein.

Please refer to FIG. 4, which is a table 40 of CQI differences andcorresponding bit values according to an example of the invention. CQIdifferences including “0”, “+1”, “−1” and “>+3” which correspond to bitvalues “00”, “01”, “10” and “11” are considered in FIG. 4. For example,if the CQI difference between a CQI and a reference CQI (i.e., CQI_ref)is “+1”, i.e., CQI-CQI_ref=1, the UE transmits the bit value “01” to thenetwork, to indicate the difference “+1” to the network. Note that thevalues and the CQI differences in the table 40 are simply used forillustrating the present invention, and can be modified according todesign considerations and system requirements.

Thus, according to the above description and the process 30, overheadneeded for transmitting the CSI report can be reduced.

Please refer to FIG. 5, which is a flowchart of a process 50 accordingto an example of the present invention. The process 50 can be utilizedin the UE shown in FIG. 1, for handling a CSI report (i.e., CSIprocess). The process 50 may be compiled into the program code 214 andincludes the following steps:

Step 500: Start.

Step 502: Omit at least one field in a CSI report, when the CSI reportcollides with another report.

Step 504: Transmit the CSI report to the network.

Step 506: End.

According to the process 50, the UE first omits (e.g., removes) at leastone field in a CSI report, when the CSI report collides with another CSIreport. Then, the UE transmits the CSI report to the network. In otherwords, the UE may further compress the CSI report and transmit thecompressed CSI report to the network, since the at least one field isomitted. Thus, overhead needed for transmitting the CSI report can bereduced.

Realization of the process 50 is not limited. For example, the CSIreport may correspond to a component carrier. That is, when the UEcommunicates with the network via multiple component carriers accordingto the CA, the UE needs to feed back the CSI reports corresponding tothe component carriers to the network. For one of the CSI reports, theUE first omits one or more fields in the CSI report, and transmit theCSI report to the network. In another example, the CSI report maycorrespond to a transmission point in the network. That is, when the UEcommunicates with multiple transmission points in the network accordingto the CoMP, the UE needs to feed back the CSI reports corresponding tothe transmission points to the network. In this situation, the CSIreports may include channel information between the UE and thetransmission points. Similarly, for one of the CSI reports, the UE firstomits one or more fields in the CSI report, and transmit the CSI reportto the network. In another example, the CSI report may correspond to aCoMP configuration, wherein a CoMP configuration may be the jointtransmission, the dynamic point selection, the CS/CB or the dynamicpoint blanking. In addition, different CSI reports may correspond to thesame CoMP configuration with the same, partly different or differentrealizations. After the network receives the CSI report, the network candetermine that the at least one field is the same as at least onecorresponding field in a reference CSI report. Preferably, the referenceCSI report is transmitted to the network, before transmitting the CSIreport to the network.

Note that detail of the at least one field in the CSI report mentionedabove is not limited. For example, the at least one field may include aCQI, a PMI, a RI and/or a PTI. For example, the CSI report may includethe fields which are the CQI, the PMI and the RI. However, the CSIreport may collide with another CSI report. According to the presentinvention, the UE can omit the RI, and transmit the CSI report includingthe PMI and the CQI to the network. After the network receives the CSIreport with the omitted RI, the network can determine that the RI of theCSI report is the same as a RI of a reference CSI report.

Thus, according to the above description and the process 50, overheadneeded for transmitting the CSI report can be reduced.

Please refer to FIG. 6, which is a flowchart of a process 60 accordingto an example of the present invention. The process 60 can be utilizedin the UE shown in FIG. 1, for handling CSI reports (i.e., CSIprocesses). The process 60 may be compiled into the program code 214 andincludes the following steps:

Step 600: Start.

Step 602: Drop at least a first CSI report, when the at least a firstCSI report collides with at least a second CSI report.

Step 604: Transmit the at least a second CSI report and an indicator tothe network, wherein the indicator indicates the at least a first CSIreport or the at least a second CSI report.

Step 606: End.

According to the process 60, the UE first drops at least a first CSIreport, when the at least a first CSI report collides with at least asecond CSI report. Then, the UE transmits the at least a second CSIreport and an indicator to the network, wherein the indicator indicatesthe at least a first CSI report or the at least a second CSI report. Forexample, when two sets of the CSI reports collide, the UE only transmitsone set of the CSI reports to the network, and the other set of the CSIreports is dropped. Further, the UE also transmit an indication to thenetwork, when transmitting the set of the CSI reports. For example, theindication may indicate the transmitted set of the CSI reports. Inanother example, the indication may indicate the dropped set of the CSIreports. Thus, the network can recognize the transmitted set of the CSIreports and the dropped set of the CSI reports according to theindication. As a result, collision between the CSI reports can beavoided.

Realization of the process 60 is not limited. For example, the at leasta first CSI report and the at least a second CSI report may correspondto a plurality of component carriers, respectively. That is, when the UEcommunicates with the network via multiple component carriers accordingto the CA, the UE needs to feed back the CSI reports corresponding tothe component carriers to the network. When two CSI reports collide, theUE may drop the first CSI report, and transmit the second CSI report andan indication to the network, wherein the indication may indicate thefirst CSI report or the second CSI report. In another example, the atleast a first CSI report and the at least a second CSI report maycorrespond to a plurality of transmission points of the network,respectively. That is, when the UE communicates with multipletransmission points in the network according to the CoMP, the UE needsto feed back the CSI reports corresponding to the transmission points tothe network. In this situation, the CSI reports may include channelinformation between the UE and the transmission points. Similarly, whentwo CSI reports collide, the UE may drop the first CSI report, andtransmit the second CSI report and an indication to the network, whereinthe indication may indicate the first CSI report or the second CSIreport. In another example, the at least a first CSI report and the atleast a second CSI report may correspond to a plurality of CoMPconfigurations, respectively, wherein a CoMP configuration may be thejoint transmission, the dynamic point selection, the CS/CB or dynamicpoint blanking. In addition, different CSI reports may correspond to thesame CoMP configuration with the same, partly different or differentrealizations.

Note that detail of a CSI report mentioned above is not limited. Forexample, the CSI report may include one or more fields which may includea CQI, a PMI, a RI and/or a PTI. On the other hand, the indicatormentioned above may include at least one identity corresponding to theat least a first CSI report or the at least a second CSI report. Forexample, the indicator may include an identity of a dropped CSI reportfor indicating the dropped CSI report, or an identity of a transmittedCSI report for indicating the transmitted CSI report. A method accordingto which the UE determines that the first CSI report and the second CSIreport collide is not limited. For example, the UE may determine thatthe first CSI report and the second CSI report collide, when the firstCSI report and the second CSI report collide are scheduled to betransmitted via the same resource (e.g., the same subframe, the sameresource blocks, etc).

Thus, according to the above description and the process 60, collisionbetween the CSI reports can be avoided.

Those skilled in the art should readily make combinations, modificationsand/or alterations on the abovementioned description and examples. Theabovementioned steps of the processes including suggested steps can berealized by means that could be a hardware, a firmware known as acombination of a hardware device and computer instructions and data thatreside as read-only software on the hardware device, or an electronicsystem. Examples of hardware can include analog, digital and mixedcircuits known as microcircuit, microchip, or silicon chip. Examples ofthe electronic system can include a system on chip (SOC), system inpackage (SiP), a computer on module (COM), and the communication device20.

To sum up, the present invention provides a device for handling CSIreports. Overhead needed for transmitting the CSI report can be reduced,and collision between the CSI reports can be avoided. Thus, performanceof the wireless communication system can be improved.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A communication device for handling periodicchannel state information (CSI) reports, comprising: a storage unit forstoring instructions of: determining at least one field differencebetween a reference CSI report and at least one periodic CSI report,wherein the at least one periodic CSI report corresponds to at least onecomponent carrier, respectively; transmitting the reference CSI reportto a network; and transmitting the at least one field difference to thenetwork; and a processing means, coupled to the storage unit, configuredto execute the instructions stored in the storage unit.
 2. Thecommunication device of claim 1, wherein each of the at least oneperiodic CSI report comprises at least one field which comprises atleast one of a Channel Quality Indicator (CQI), a Precoding Matrix Index(PMI), a Rank Indicator (RI) and a Precoder Type Indicator (PTI).
 3. Thecommunication device of claim 1, wherein the instruction of transmittingthe at least one field difference to the network further comprises:determining at least one value corresponding to the at least one fielddifference according to a predetermined table; and transmitting the atleast one value to the network.
 4. The communication device of claim 1,wherein each of the at least one value is represented by at least onebit.
 5. A communication device for handling a periodic channel stateinformation (CSI) report, comprising: a storage unit for storinginstructions of: omitting at least one field in a periodic CSI reportcorresponding to a component carrier, when the periodic CSI reportcollides with another CSI report; and transmitting the periodic CSIreport to a network; and a processing means, coupled to the storageunit, configured to execute the instructions stored in the storage unit.6. The communication device of claim 5, wherein the network determinesthat the at least one field is the same as at least one correspondingfield in a reference CSI report.
 7. The communication device of claim 6,wherein the reference CSI report is transmitted to the network, beforetransmitting the periodic CSI report to the network.
 8. Thecommunication device of claim 5, wherein the at least one fieldcomprises at least one of a Channel Quality Indicator (CQI), a PrecodingMatrix Index (PMI), a Rank Indicator (RI) and a Precoder Type Indicator(PTI) in the periodic CSI report.
 9. A communication device for handlingperiodic channel state information (CSI) reports, comprising: a storageunit for storing instructions of: dropping at least one first periodicCSI report, when the at least one first periodic CSI report collideswith at least one second periodic CSI report, wherein the at least onefirst periodic CSI report and the at least one second periodic CSIreport correspond to a plurality of component carriers, respectively;and transmitting the at least one second periodic CSI report to anetwork; transmitting an indicator to the network, wherein the indicatorindicates which CSI report is dropped or which CSI report istransmitted; and a processing means, coupled to the storage unit,configured to execute the instructions stored in the storage unit. 10.The communication device of claim 9, wherein each of the at least onefirst CSI report and the at least one second CSI report comprises atleast one of a Channel Quality Indicator (CQI), a Precoding Matrix Index(PMI), a Rank Indicator (RI) and a Precoder Type Indicator (PTI). 11.The communication device of claim 9, wherein the indicator comprises atleast one identity corresponding to the at least one first periodic CSIreport or the at least one second periodic CSI report.
 12. Thecommunication device of claim 9, wherein the at least one first periodicCSI report collides with the at least one second periodic CSI report,when the at least one first periodic CSI report collides with the atleast one second periodic CSI report are scheduled to be transmitted viathe same resource.